Low visibility, wet runway must have led to poor braking action

Low visibility, wet runway must have led to poor braking action

Manju.V@timesgroup.com

Mumbai:09.08.2020

Flight IX-1344’s problems appear to have begun during its descent in heavy rains, with difficulty in spotting the runway from the cockpit. What followed was a host of factors which could have forced the pilots to opt to land in unfavourable tailwinds on a wet runway and face problems with the braking action, leading to the crash.

It began well with the pilots overflying the runway to line up for an approach to land on runway 28, according to data from flightradar24, a live flight tracking app.

The norm is to land an aircraft into the wind and runway 28 had headwinds, favourable for safe landing. But during the descent, the pilots appear to have encountered their first problem with weather. Aviation weather report (METAR) for that time showed few light clouds at 300 feet. “The pilots probably couldn’t spot runway 28 by the time the aircraft descended to 265 feet above ground level. For Calicut airport, this is the height at which pilots have to discontinue the descent to land and carry out a go-around if the runway isn’t in sight,’’ said a senior commander.

The pilots then decided to land from the opposite end, that is on runway 10. They have to seek permission from the air traffic controller, who in turn, consults METAR for wind speed and direction.

“If the runway has tailwinds of 15kt or higher, it isn’t considered safe for landing,” said a senior commander. Other pilots said a tailwind of more than 10kt for a table-top runway should be considered unsafe for landing. The METAR report for the time of accident showed a windspeed of 12kt from ‘direction 260.’ It essentially translates to a tailwind of 11kt for runway 10. But they also spoke about possible inaccuracies in the METAR report.

For instance, in August 2017, a SpiceJet aircraft went off the runway during landing at Calicut airport. The investigation report noted that METAR showed zero winds at the time of the incident, but the flight crew experienced winds over 12-15kt. “From the position of the wreckage it does look like the aircraft landed in tailwinds that were stronger than what METAR reported,” said an examiner on B737 aircraft.

There are other crucial questions. The photographs of the wreckage shows the aircraft wings with speed brakes not deployed. The senior commander said: “Were the spoilers, the flaps that lift over the wing to slow down an aircraft, deployed during landing? If they are not deployed, the aircraft won’t slow down. But the AIX commander appears to have switched off the engines. After all, he was an IAF pilot, he would have had the presence of mind to switch off the engine and prevent a possible fire following the impact.’’ Another factor that a number of pilots spoke about was ‘aquaplaning’, which refers to a condition wherein a layer of water builds between aircraft wheel and runway surface leading to loss of braking action.

“Apart from aquaplaning, if there are significant rubber deposits, then the braking action would be really poor,” said the examiner.

Pilot fatigue is another crucial aspect that needs to be looked into, said AIX pilots who added that Vande Bharat Mission flights, by their very nature of being repatriation flights, involve doing extra duty time.